Loss in quality when colour correcting/ grading footage

I'm working on footage shot on a Canon 7D in Premiere Pro. I find when I push the grade, there's a significant loss in quality. I don't believe I'm pushing anything too much in post, just lots of small tweaks like shadows/highlights, contrast, curves etc (I make a point to never push very far with anything) but I'm still noticing a loss in quality after exporting in the 'Match Source - High Bitrate' preset.

Is there anything I can do to keep the quality high? transcode the footage or export in different settings? or should I avoid certain tweaks when grading?

The image quality of that camera in terms of pixels & colors is just good enough to fool the human eye but not a computer. You can't mess much with color correction at all. When you do, the image quality goes south. If you like to color correct, you'll need a camera that creates better files than crummy H.264.

Converting to ProRes or DNxHD...10-bit codecs...will allow you to push things a little more, as you now are in a 10-bit space, and not 8 bit (even though the footage still is 8-bit) You can push things a LITTLE more. But no, H.264 doesn't lend itself to drastic color grading.